Poster P10 - Development of a Finite Element Model of a Neonate

Introduction: Due to the ethical limitations in investigating fetal injuries during complicated birthing scenarios such as shoulder dystocia (SD), computational models can offer a valuable alternative for understanding injury mechanisms and developing preventative strategies. Current rigid-body fetal models provide insights into SD-related injuries but lack soft tissue and detailed bony structures [1]. This study aims to develop a biofidelic three-dimensional finite element model (3D-FEM) of a neonate to address these limitations and enable comprehensive and accurate simulations of neonatal injuries during SD.

Materials and

Methods: Geometry Development: A1.5-year-old, pediatric model was adapted from an open-source license: Position and Personalize Advanced Human Body Models for Injury Prediction (PIPER) project. This PIPER model (available at piper-project.org/downloads) was scaled down to the size of a 90th percentile neonate based on bisacromial diameter [1]. Biomechanical Properties: The neonate’s skull and body were assumed to be linearly elastic with an Elastic Modulus of 2500 MPa and a Poisson Ratio of 0.22, while other structures inherited the material properties of the original PIPER model [2]. Grid Independence Test: Two convergence studies were performed using LS-Prepost 4.8 (Ansys, Inc., Canonsburg, PA) to determine appropriate element sizes for the head and neonate body, maximizing computational efficiency. A compression test of 100 N was performed on a constrained 3D-FEM sphere mimicking the PIPER skull model dimensions with varying hexahedral element sizes (40 mm–10 mm). Similarly, a compression test of 100 N was performed on a 3D-FEM rectangular prism, mimicking the neonate body dimensions, impacting a 3D-FEM surrogate of the pubic symphysis with varying element sizes (40 mm–5 mm). Mesh Development: Once element size ranges were determined, ICEM-CFD 2022 R2 (Ansys, Inc., Canonsburg, PA) was used to block-mesh the geometry until a hexahedral mesh was generated to accurately represent a neonatal 3D-FEM.

Results, Conclusions, and Discussions: A progressive reduction in compressive stress variation with decreased element size was observed for the fetal head, with an efficient element size range of 15 mm–25 mm (Fig. 1A). Similarly, such a reduction in compressive stress variation was observed during shoulder impaction of the neonate body, with an efficient element size range of 5 mm–30 mm (Fig. 1B). A high-quality hexahedral 3D-FEM (61,577 elements) was generated with quality metrics displayed (Fig. 1C, D). This study is the first to model the neonate with FE techniques by rigorously validating the element sizes and mesh quality for such model This 3D-FEM can serve as a useful tool to provide quantitative metrics for the assessment of neonate injuries during SD.

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